Among the various video display systems available in the art, an optical projection system is known to be capable of providing a high quality display in a large scale. In such an optical projection system, light from a lamp is uniformly illuminated onto an array of, e.g., M.times.N, actuated mirrors such that each of the mirrors is coupled with each of the actuators. The actuators may be made of an electrodisplacive material such as a piezoelectric or an electrostrictive material which deforms in response to an electric field applied thereto.
The reflected light beam from each of the mirrors is incident upon an aperture of a baffle. By applying an electrical signal to each of the actuators, the relative position of each of the mirrors to the incident light beam is altered, thereby causing a deviation in the optical path of the reflected beam from each of the mirrors. As the optical path of each of the reflected beams is varied, the amount of light reflected from each of the mirrors which passes through the aperture is changed, thereby modulating the intensity of the beam. The modulated beams through the aperture are transmitted onto a projection screen via an appropriate optical device such as a projection lens, to thereby display an image thereon.
In FIG. 1, there is shown a cross sectional view of an array 10 of M.times.N thin film actuated mirrors, e.g., 5a, 5b and 5c, for use in an optical projection system, disclosed in a copending commonly owned application, U.S. Ser. No. 08/331,399, entitled "THIN FILM ACTUATED MIRROR ARRAY AND METHOD FOR THE MANUFACTURE THEREOF", comprising: an active matrix 11 including a substrate 12, an array of M.times.N transistors (not shown) and an array 13 of M.times.N connecting terminals, e.g., 14a 14b and 14c; an array 15 of M.times.N thin film actuating structures, e.g., 16a, 16b, and 16c, each of the actuating structures 16 having at least a thin film layer 17 of a motion-inducing material, a first electrode 18 and a second electrode 19, the first and second electrodes being placed on top and bottom of the thin film motion-inducing layer 17, respectively; an array 20 of M.times.N supporting members, e.g., 21a, 21b and 21c, each of the supporting members, e.g., 21a, being used for holding the corresponding actuating structure 16a in place by cantilevering thereof and also for electrically connecting the corresponding actuating structure 16a and the active matrix 11; and an array 22 of M.times.N mirrors, e.g., 23a, 23b and 23c, for reflecting light beams, each of the mirrors being placed on top of each of the actuating strctures 16. In the thin film actuated mirror array 10, an electrical signal is applied across the thin film layer 17 of the motion-inducing material located between the pair of electrodes 18, 19 in each of the actuating structures, e.g., 16a, causing a deformation thereof, which will in turn deform the mirror 23a placed on top thereof, thereby changing the optical path of the incident light beam.
One of the major problems associated with the above described thin film actuated mirror array is the overall optical efficiency of the array 10. When each of the actuating structures, e.g., 16a deforms in response to the electric field applied across the thin film motion-inducing layer 17 thereof, the mirror 23a attached thereto also deforms. However, in the array 10, the portion of the mirror 23a secured to the supporting member 21a does not deform in respose to the electric field, but remains securely in place, and furthermore, the portion of the mirror that deforms bends to thereby create a curved top surface from which the light beams are reflected. As a result, the overall optical efficiency of the array 10 decreases, as well as, by the effective length of the mirror 23a being reduced by the length of the portion of the actuating structure secured to the supporting member 21a, but also by the curved top surface of the mirror 23a when it bends.